Vitamin A supplementation during pregnancy.
BACKGROUND: Vitamin A supplements have been recommended in pregnancy to improve outcomes that include maternal mortality and morbidity. OBJECTIVES: To review the effectiveness of vitamin A supplementation during pregnancy, alone or in combination with other supplements, on maternal and newborn clinical and laboratory outcomes. SEARCH STRATEGY: We searched the Cochrane Pregnancy and Childbirth Group's specialised register of controlled trials (April 2002) and the Cochrane Controlled Trials Register (The Cochrane Library Issue 1, 2002). SELECTION CRITERIA: All randomised or quasi-randomised trials evaluating the effect of vitamin A supplementation in pregnant women. The types of intervention included vitamin A supplementation alone or in combination with other micro-nutrients. DATA COLLECTION AND ANALYSIS: We assessed trials for methodological quality using the standard Cochrane criteria of adequacy of concealment. At least two reviewers independently assessed the trials for inclusion and extracted data. We collected information on blinding, loss to follow-up, setting, number of women, exclusion after randomisation and follow-up as well as supplementation type, dose and frequency. The outcomes we sought included maternal and neonatal clinical and laboratory outcomes. MAIN RESULTS: Five trials involving 23,426 women were included. Because the trials were heterogeneous with regard to type of supplement given, duration of supplement use and outcomes measured, pooled results using meta analysis could not be performed. One large population based trial in Nepal showed a possible beneficial effect on maternal mortality after weekly vitamin A supplements. In this study a reduction was noted in all cause maternal mortality up to 12 weeks postpartum with Vitamin A supplementation (RR 0.60, 95% CI 0.37-0.97). Night-blindness was assessed in a nested case-control study within this trial and found to be reduced but not eliminated. Three trials examined the effect of vitamin A supplementation on haemoglobin levels. The trial from Indonesia showed a beneficial effect in women who were anaemic ([Hb] <11.0 g/dl). After supplementation, the proportion of women who became non-anaemic was 35% in the Vitamin A supplemented group, 68% in the iron-supplemented group, 97% in the group supplemented with both Vitamin A and iron and 16% in the placebo group. The two trials from Malawi did not corroborate these positive findings. REVIEWER'S CONCLUSIONS: Although the two trials from Nepal and Indonesia suggested beneficial effects of vitamin A supplementation, further trials are needed to determine whether vitamin A supplements can reduce maternal mortality and morbidity and by what mechanism.